IJOI Vol. 47
Periodontally-Compromised Class II Malocclusion with Early Loss of Both L6s and the UL3: Class lll Elastics for L6 Space Closure and Retraction of the Maxillary Arch with IZC Bone Screws
Drs. Huang YH, Lin JJ, Roberts WE.
Introduction
A 42 year old female presented with a periodontally compromised, skeletal Class II Division I malocclusion that was neglected because of concern about the extensive invasive treatment that was previously recommended.
Diagnosis: Bilateral full-cusp Class II malocclusion was associated with facial convexity (12o), increased lower facial height (LFH 57%), protrusive maxilla (SNA 83.5o), retrusive mandible (SNB 76o), intermaxillary discrepancy (ANB 7.5o), steep mandibular plane (FMA 44.5o), anterior openbite (2-3mm), increased overjet (7.5mm), deep curve of Spee, missing upper left canine (UR3), bilateral missing lower rst molars (LR6, LL6), and an upper dental midline that was deviated 3mm to the left. The Discrepancy Index (DI) was 69.
Etiology: Proximal cause for this severe skeletal malocclusion was the isolated loss of lower rst molars in the mixed dentition, which is pathognomonic for Molar-Incisor Hypoplasia (MIH) due to a high fever at <3 years of age. Enamel defects in a ected L6s render them susceptible to rapid destruction by caries with subsequent extraction during the mixed dentition. Lack of posterior stops in occlusion when the deciduous second molars exfoliated was a functional anomaly superimposed on an inherent tendency for facial convexity and bimaxillary protrusion. Intermaxillary crowding re ected inadequate functional expansion of the jaws. The maxilla was protrusive but not su ciently developed in width to accommodate all the teeth. This insu cent space in the upper arch resulted in a blocked-out UL3 and deviation of the upper dental midline to the left. Thus, a combination of inherent and acquired factors produced a severe skeletal malocclusion complicated by asymmetry and periodontal compromise.
Treatment: Periodontal bone loss is a stress-riser in the periodontal ligament (PDL) of orthodontically-loaded teeth. Very light forces (<1N) were applied with exible CuNiTi archwires in self-ligating brackets. Extraction in the UR4 and implant-supported prostheses to restore the missing L6s were proposed, but the patient desired conservative treatment with no implants or extractions of teeth other than the impacted UL8. Space was closed and alignment was achieved with Class IlI elastics and di erential extra-alveolar (E-A) anchorage provided by infrazygomatic crest (IZC) bone screws to retract the entire maxilla.
Results: This severe skeletal malocclusion (DI 69) was resolved with asymmetric mechanics to close space and correct the maxillary midline. Because of the missing UL3, buccal segments were Class I on the right and Class II on the left. Optimal dental correction to a CRE score of 31 was achieved with 32 months of active treatment. The L6 space closure was not retained with xed retainers because of the periodontal risk, and the spaces reopened ~1.5mm bilaterally. The patient was well pleased with the dramatic facial and dental improvement, but the skeletal and facial results may have bene tted from additional E-A anchorage screws in the mandibular buccal shelves to intrude lower molars and decrease lower facial height. However, periodontal risk precluded that option.
Conclusion: Increased experience with E-A anchorage in all four quadrants produces dramatic correction of severe skeletal malocclusions without extractions or orthognathic surgery. (Int J Orthod Implantol 2017;47:4-24)
Key words: Self-ligation appliance, Class II Division 1, midline o , excessive overjet, missing maxillary canine, early loss of lower molars, Molar- Incisor Hypoplasia (MIH), molar protraction, IZC bone screws, periodontally compromise, constricted maxilla, blocked-out maxillary canine
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MIH-Related Loss of Mandibular First Molars Resulted in an Acquired Class II Skeletal Malocclusion: Conservatively Treated with Space Closure on One Side and Implant-Supported Prosthesis on the Other
Drs. Lee A, Chang CH, Roberts WE.
Abstract
Diagnosis: A 34-year-old female presented with a Class II partially edentulous malocclusion with 4mm of overjet. Cephalometrics revealed a protrusive maxilla with relative mandibular retrusion (SNA 85°, SNB 78°, ANB of 7°). A slightly retrusive lower lip was associated with missing mandibular first molars, mesially tipped second molars, anterior spacing, and abfraction on the buccal surfaces of the lower premolars. This developmental (acquired) malocclusion is typical for bilateral Molar-Incisor Hypoplasia (MIH).
Etiology: The isolated loss of the rst molars in an otherwise healthy dentition is pathognomonic of MIH, usually due to high fever at <3 yr of age. This common childhood problem may result in developmental enamel defects, that render the rst permanent molars (6s) highly susceptible to caries soon after eruption. During the late mixed dentition, a bilateral lack of posterior centric stops in occlusion results in a typical pattern of occlusal collapse: mesially tipped second molars, deep curve of Spee, mandibular retrusion, and incisal compensation (increased overjet and/or deep bite).
Treatment: Full- xed non-extraction treatment was indicated to close the lower right (LR) space, but the lower left (LL) space required preparation for an implant-supported prosthesis because of the missing left third molar. The mesially tipped mandibular molars were uprighted with a copper-nickel-titanium archwire (CuNiTi), open coil springs, and a more gingival orientation of the second molar tubes on the mesial side. During LR space closure, the midline was maintained with an asymmetric Class II elastic in a L-con guration; the elastic coursed from the upper right canine (UR3), passed gingival to the hook on the LR second premolar (LR5) and extended to the LR second molar (LR7). Symmetrical Class II elastics in the same configuration were used bilaterally to resolve the Class II relationship after the LR space was closed. At 17 months of active treatment, an implant was placed to restore the LL6. Following a 6 month healing phase, the implant was uncovered and a healing abutment was placed. To prevent relapse, xed appliances were not removed until the temporary prosthesis was placed. The nal crown was delivered at 23 months.
Results: This di cult malocclusion was treated to an appropriate preprosthetic result in 17 months, and nal nishing was achieved after the implant was placed. The cephalometric film documented asymmetric sagittal positions of the TMJs, but transcranial radiographs of the joints in the open and closed positions were within normal limits (WNL). Overall, interdisciplinary treatment for this complex problem with a Discrepancy Index score of 24, was treated to a Cast-Radiograph Evaluation score of 19 and a Pink & White Esthetic Score of 3 in 23 months. At two-year follow-up, occlusal contacts were optimal, the Class I correction was stable, and the pro le had continued to improve. All morphology and function was WNL.
Conclusions: MIH can result in challenging symmetric or asymmetric malocclusions that have good potential for conservative skeletal correction. De ning the etiology is an important diagnostic procedure because MIH-related functional retrusion responds well to bite turbos and Class II elastics with an L-con guration. There was no need for functional orthopedics, extractions, temporary anchorage devices, or surgery. (Int J Orthod Implantol 2017;47:26-48)
Key words: Molar-Incisor Hypoplasia (MIH), missing rst molar, mesially tipped molar, molar uprighting, implant site preparation, asymmetrical mechanics, space management, implant-supported prosthesis
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Skeletal Class III Crowded Malocclusion Treated with the Insignia® Custom Bracket System
Drs. Lee A, Chang CH, Roberts WE.
Abstract
Chief Complaint (CC): A 18-year-old female presented with a CC of poor personal con dence due to an unesthetic smile.
Diagnosis and Etiology: Facial form was concave (G-SN-Pg’ -3o) with decreased, but acceptable lip protrusion (E-Line -2/-1mm). An intermaxillary discrepancy of ANB -2o was the sum of slight maxillary de ciency (SNA 81o) and modest mandibular protrusion (SNB 83o). The maxillary arch was asymmetric: (1). Class I on the right, (2). 4mm Class III on the left, (3). 3mm anterior crossbite, and (4). 2mm upper midline deviation to the right. Both arches were functionally underdeveloped which was manifest as severe dental crowding of -10mm/-6mm in the upper and lower arches, respectively. The intermaxillary arch length de ciency resulted in mesial- out rotation of the lower canines, and the upper canines were blocked out to the labial.
Treatment: The Insignia® system was utilized to digitally plan an ideal intermaxillary alignment, following extraction of all four 1st premolars, that was based on the 3D image of each tooth. The digital set-up was then reverse engineered to construct a full xed, self-ligating appliance with a custom bracket for each tooth, that produced ideal alignment once the full size archwires were placed. Each tooth was bonded with a custom jig designed for ideal positioning of the bracket on each tooth. This digital method is designed to eliminate repositioning of brackets and archwire adjustments. Comprehensive treatment with progressive stock and custom archwires was accomplished with 10 appointments in 15 months. One nishing bend was required during the detailing phase because of a preventable error during the pre-treatment digital set-up.
Outcomes: The excellent alignment, comfortable occlusion, and pleasing smile substantially increased the patient’s poise and personal confidence. This skeletal Class III malocclusion, with a Discrepancy Index (DI) of 28, was treated in 15 months to a Cast- Radiograph Evaluation (CRE) of 16 and a Pink & White Esthetic Score of 1.
Conclusion: Insignia® is a precise method for a direct path to outstanding clinical outcomes with minimal chair time, adjustments and treatment duration. The rate of tooth movement is enhanced, and the incidence of root resorption is reduced, by controlling PDL stress and repetitive episodes of necrosis via progressive relatively exible archwires, that require few if any detailing adjustments. (Int J Orthod Implantol 2017;47:52-69)
Key words: Insignia® system, digital bracket positioning, passive self-ligating bracket, archwire sequence, custom bracket, custom torque, low periodontal ligament (PDL) stress, necrosis, ectopic eruption, Class III malocclusion, crowding, occlusal bite turbo, dental esthetics
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Simplified Mechanics for Gummy Smile Correction
Drs. Lin C, Wu Y, Chang CH, Roberts WE.
Abstract
This case report describes the interdisciplinary treatment of a 25-year-old woman presenting with chief complaints of bimaxillary protrusion and excessive gingival display (“gummy smile”). She was dissatisfled with her previous non-extraction orthodontic treatment, rendered at age 10. The Discrepancy index (DI) for this severe malocclusion was 21. Orthodontic treatment involved extraction of four premolars to correct protrusion, and skeletal anchorage via four miniscrews (2 anterior and 2 posterior) to intrude the entire maxillary arch. Space closure utilizing maxillary extra-alveolar (E-A) bone screws reduced lip protrusion and the anterior miniscrews were used to intrude the maxillary incisors. Following orthodontics, surgical crown lengthening was performed in the maxillary anterior segment. 32 months of interdisciplinary treatment resulted in a near ideal result as evidenced by a Cast-Radiograph Score (CRE) of 15 and Pink & White (dental esthetic) score of 3. (Int I Ortho Implantol 2017;47:72-91)
Key words: Class I malocclusion, bimaxillary protrusion, surgical crown lengthening, self-ligating appliance, gummy smile
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Comparison of the Failure Rate for Infra- Zygomatic Bone Screws Placed in Movable Mucosa or Attached Gingiva
Drs. Hsu E, Lin JSY, Yeh HY, Chang CH, Roberts WE.
Abstract
Objective: Compare the six-month failure rates for infra-zygomatic crest (IZC) bone screws inserted into movable mucosa (MM) or attached gingiva (AG). The hypothesis was that MM would have a higher failure rate than AG.
Materials and Methods: A total of 386 patients (76 males and 310 females; mean age, 24.3 years; aged from 10 to 59 y/o) were treated with a 2x12mm IZC OBS (OrthoBoneScrew® Newton’s A Ltd, Hsinchu City, Taiwan), bilaterally. Pairs of stainless steel (SS) and Ti alloy (TA) screws were randomly assigned as to side. All OBSs were positioned in the lateral aspect of the alveolar process, buccal to the upper rst and second molar roots, by the same clinician (C.C.). All OBSs were placed at an angle of about 70 degrees above the horizontal (extra-alveolar approach) to achieve maximum bone engagement. Screw heads were positioned at least 5mm above the level of the soft tissue to facilitate oral hygiene. All OBSs were immediately loaded with pre-stretched elastomeric modules ranging from 8-oz to 14-oz (227–397 g or 223–389 cN), according to the patients’ age and bone density. The clinician decided on the applied load according to clinical requirements, and the perception of the bone mass and density supporting the OBS. Six months after each screw was placed, it was routinely evaluated for mobility, ability to maintain continuous anchorage during the 6 month period, and type of mucosa penetrated by the tip of the OBS as it was installed. All 772 consecutively placed IZC OBSs in 386 patients were assessed for the soft tissue e ect. SS vs. TA failure rate will be reported separately.
Results: 387 were placed in MM and 385 were in AG. 49 out of 772 miniscrews failed (6.35%), 25 of which were in MM (6.46%), and 24 were in AG (6.23%); there was no statistically signi cant di erence at the p<.05 level. There was no signi cant relationship between failure and the initial applied load. Failures were unilateral in 21 patients and bilateral in 14 patients. The failure rate on the right side (6.48%) was slightly higher than the left (6.22%), but the di erence was not statistically signi cant. Patients with screw failures were 12-43 yr old, mean age of 24.2 yr, which was insigni cant compared to the demographics of the entire sample.
Conclusion: Infra-zygomatic crest, bone screws, skeletal anchorage, movable mucosa, attached gingiva, extra-alveolar orthodontic anchorage
Key words:Insignia system, passive self-ligating bracket, custom bracket, CBCT
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Rebonding Tips for the Custom Bracket System: Insignia®
Drs. Chang C, Lee A, Chang CH, Roberts WE.
Abstract
Bracket-positioning jigs are crucial for guiding precise, indirect bonding of Insignia® brackets. There are three tips to successfully rebond the Insignia® brackets with proper application of jigs and brackets.
Tip 1: Carefully check residual resin on the bracket base and the tooth surface. Identify potential dislodgement factors and eliminate them.
Tip 2: Use a customized single jig, not the group jig, to precisely position the bracket on the tooth surface.
Tip 3: Before setting resin with light-curing, press down the corner of jig with a nger and ensure the bracket base securely tted onto the tooth surface with the tip of a scaler or explorer. (Int J Orthod Implantol 2017;47:110-113)
Key words: Insignia® system, passive self-ligating bracket, custom bracket, indirect bonding, bracket-positioning jig
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